This application claims to benefit of Korean Patent Application No. 2002-12004, filed Month day, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a brushless vibration motor generating a receiving or alarm signal in a mobile telecommunication unit, such as a wireless phone, and more particularly, to a brushless vibration motor being capable of improving durability, vibration characteristics, a load reduction, and rotation characteristics using an improved shaft structure and a rotor assembling structure.
2. Description of the Related Art
According to a rapid development of digital technology, various types of wire or wireless telecommunication machines have been developed and widely used. Developments of wire or wireless telecommunication technologies provides machines facilitates transmission of huge amount of various information data in a very short period of time, thereby enabling the users to transmit and receive desirable information data regardless of a location and time. A wide and rapid transmission flow of the information data forms a global town with a development of transportation.
One of the wireless telecommunication machines is a personal mobile telecommunication terminal, such as a cellular phone or a personal communication system PCS. The cellular phone is one of digital or analog short wave transmission types connecting a mobile telephone to a transmitter/receiver of which service area is called a cell.
Although the PCS is the same wireless service system as the cellular phone, the PCS provides mobility for personal use. The PCS is also called to a digital cellular phone for a mobile user and requires a great number of antennas covering various service areas. A closest antenna is supposed to be used to receive/transmit a signal from/to the PCS and transmit the signal to a wireless network station.
A cellular system operates in a frequency band ranging 824-849 MHz, and the PCS operates in a frequency band ranging 1850-1990 MHz. Since the PCS has a data transmission rate of 8-13 Kbps, a high speed data transmission is almost impossible. According to the development of digital telecommunication technologies, a more high speed transmission of data packet, video, multimedia enables a personal telecommunication to receive various services, such as a voice telephone, telex, wireless calling, electronic mail, etc.
In accordance with the development of the telecommunication technologies and parts, integration and miniaturization of electronic products, and multifunctional system, telecommunication terminals employs various types of equipment, such as a digital camera transmitting a digital image, an audio unit generating a receiving call with a high quality and a multiple channel, a display device displaying an image using a high resolution, a wide viewing angle, and a high response time.
An alarm is realized in a bell sound mode or a vibration mode to generate the calling signal of a received call, a received electronic mail, and a predetermining time. Bell sound of the bell sound mode is stored in the mobile telecommunication terminal in a manufacturing process or downloaded through Internet connected to the telecommunication terminal. The vibration mode is performed using a vibration motor having a rotor. The vibration motor currently used in a mobile telecommunication terminal is one of a brush vibration motor and a brushless vibration motor or one of a bar type vibration motor and a coin type vibration motor.
A conventional brush vibration motor having a coil type used in the mobile telecommunication terminal is shown in FIG. 1. A structure and an operation of the conventional brush vibration motor is described hereinafter, and then a conventional brushless vibration motor removing problems occurring in the conventional brush vibration motor will be described later.
FIG. 1 is a cross-sectional view of a brush-type vibration motor, FIG. 2 is an exploded view of the brush-type vibration motor shown in FIG. 1, and FIGS. 3A and 3B are a plan view showing an arrangement of a coil and a commutator contacting a brush of the brush-type vibration motor shown in FIGS. 1 and 2.
As shown in FIGS. 1 and 2, a bracket 1 having a fixed plate (base plate) is formed with a burring element (not indicated with a reference numeral) extended upward from a center portion of the bracket 1, and a shaft 5 includes a first end inserted into the burring in a vertical direction and fixedly coupled to the bracket 1 using a washer. A flexible printed circuit board (FPCB) 2 is mounted in an upper surface of the bracket 1, and a predetermined circuit and a terminal unit are formed on the FPCB2.
A magnet 3 having a ringxe2x80x94shape is mounted on an upper surface of the FPCB2 of the bracket 1 around a shaft 5. The magnet 3 includes a plurality of magnet poles having one of N and S polarities. A brush 4 is connected to the FPCB2 at one end and contacts one of segments of a commutator of a rotor 10 at the other end which is disposed above an upper surface of the magnet 3.
The rotor 10 is rotatably disposed around the shaft 5. The rotor 10 includes a counterweight 13 generating eccentricity for vibration of the motor, coils 12 through which alternative current flows, a bearing reducing friction between the shaft 5 and the rotor 11, and a resin formed in a single body insertion injected method as an insulation material.
The counterweight 13 is mounted on a portion of the rotor 10 to generate the eccentricity and the coils 12 is disposed on the rotor 10 in a circular direction of the shaft 5 to generate a magnetic field upon receipt of the alternative current from the commutator. The rotor 10 includes the bearing inserted around the shaft 5 and is formed in a monolithic body by filling the space with the resin as the insulation material.
A shape of the rotor 10 varies according to a desirable vibration type in the vibration motor. The number of the coils 12 is also variable as well as an arrangement of the coils 12 according to a motor driving method. If the arrangement of the coils 12 and the magnetic poles of the magnet 3 are changed, a rotation electromagnetic force occurring due to the magnetic field generated between the coils 12 and the magnet 3 is changed, and accordingly, a torque and a rotation speed of the rotor 10 are changed. In a three phase driving methods. The number of the coils is a multiple of 3.
A printed circuit board 14 is mounted on a bottom surface of the rotor 10, and the commutator having the segments is mounted on the printed circuit board 14 to supply the current to the coils 12. When the rotor 10 rotates, respective segments of the commutator contact the brush 4 according to a rotation position of the commutator corresponding to the brush.
A cover 20 having a cap shape and an inner portion fixedly supporting a distal end of the shaft 5 is connected to a circumference of the bracket 1 to enclose the rotor 10 and the magnet 3.
An operation of the brush vibration motor having the above structure is explained hereinafter. The current flows through the brush 4 and the coils through the segments of the commutator contacting the brush 4. The coils 12 are excited upon receipt of the current, and the magnetic field is generated in the coils 12 through which the current flows according to Fleming""s rule. The rotation electromagnetic force is generated when the magnetic force of the coils 12 is offset with another magnetic field generated from the magnet 3 having the magnetic poles.
The rotor 10 starts to rotate in accordance with the rotation electromagnetic force generated between the coils 12 and the magnet 3. When the brush 4 contacts different segments of the commutator, the coils 12 are turned on an off, and accordingly a change of the rotation electromagnetic force maintain the rotor rotating.
Since the rotor 10 eccentrically rotates due to the existence of the counterweight 13, a predetermined vibration is generated to make the wireless phone unbalanced (vibrated), and accordingly, the user of the wireless phone acknowledges he receiving call.
The above brush vibration motor is disadvantageous since durability of a mechanical contact between the commutator and the brush deteriorates, and an assembling problem in a manufacturing process occurs. That is when friction occurs between the brush and the commutator, metal power or lead power is scattered, and a lifespan of the motor becomes shortened. Moreover, due to arc generated from a point contact in a warn-out portion of the brush and the commutator, a flash over phenomenon may occur, and fire may be set in the motor.
In an effort to solve the above problems, a brushless vibration motor has been developed and is currently in widespread use. In the brushless vibration motor, the mechanical contact between the commutator and the brush is replaced with an integrated circuit, e.g., a semiconductor I.C., to perform an electronic and non-contacting rectifying process.
The non-contacting rectifying process can be obtained through a magnetic or optical method. Generally, since the rotor is formed with a permanent magnet, a hall element is used to detect a position of the rotor using the magnetic field generated from the rotor. Thus, it is not necessary to provide any additional parts generating a specific magnetic field.
When a structure of the motor becomes simplified, noise is not generated and durability and an assembling process are improved. The brushless motor, however, may be not advantageous in a manufacturing cost since an electronic parts driving and controlling a motor should be installed in the motor.
That is, the conventional brushless vibration motor is advantageous in a high precision and a high reliability, but disadvantageous since the electronic parts are additionally needed, and the manufacturing cost increases.
The conventional brushless motor may have other problems in an assembled structure of the rotor. In the conventional brushless motor, the rotor is formed with the coils the counterweight, and the bearing contacting the shaft with friction by using a bonding process. Thus, the assembled structure of the rotor cannot be secured in axial and radial directions of the shaft.
Accordingly, strength and durability of the motor is weakened, the motor is susceptible to an external impact. Due to an unstable rotation of the motor during an eccentric rotation, vibration sound may be not generated uniformly to notify a user of the receiving all. A maintenance cost for repair or replacement of respective parts increases.
Since the rotor of the brushless vibration motor is manufactured by the insertion injection method, the manufacturing cost increases. Due to a weight an injection molding material filled in the coils, desirable characteristics of the rotation electromagnetic force and stable rotational movement cannot be obtained, and the problems of wear and tear between the brush and the commutator still exist.
The conventional brushless motor may lacks compatibility between wireless phones when driving methods of the vibration motor are not the same but different from each other.
The electronic parts of the motor should be replaced with another one according to the driving method of the motor. In the conventional wireless phone, the electronic parts controlling the motor are separately mounted on the wireless phone from the motor. Accordingly, when the motor is replaced, the electronic part should be replaced as well according to the driving method of the motor, thereby lowering the compatibility and reducing an efficiency of the motor in view of a manufacturer and the wireless phone user.
Therefore, in order to solve the problem that the electronic parts are replaced in accordance with the driving method of the motor, technologies for mounting the electronic parts in an inside of the motor are developed.
However, the coils forming a stator is not mounted on the same area as the bracket plate but a separate area different from the area of the fixed plate. Since an empty space on the bracket other than the area in which the coils are mounted, cannot be used, a size and a diameter of the bracket increase.
When the electronic parts are mounted on a lower surface of the bracket, a height of the motor may increase, and the motor cannot be minimized.
Another disadvantage in the conventional brushless vibration motor is a non-motive point at which a uniform torque to rotate the rotor does not generate from the coils and the magnet, thereby preventing the rotor from rotating.
At the non-motive point, a center of the magnetic polarity of the magnet becomes identical to that of the coil, and the torque becomes zero. In the three phases driving method, all torque generated from respective phases are added so as not to be zero. Thus, a total torque does not become zero, and there does not exist the non-motive point.
However, the three phase driving method includes a complicated driving circuits compared to the mono phase driving method. The size of the motor becomes large, and the manufacturing cost increases. Therefore, it is necessary to eliminate the non-motive point in the mono phase driving method and reduce the manufacturing cost of the brushless vibration motor.
It is desirable to improve the assembled structure of the rotor and generate on effective vibration while maintaining liability and reliability vibration motor. It is also desirable to improve minimization and compatibility of the motor and remove the non-motive point from the motor using the mono phase driving method. In addition to the improvement on the assembled structure of the rotor, a structure of the shaft disposed at a rotational center of the rotor needs to be improved to provide a stable rotation of the rotor, a load and a power consumption are needed to be reduced while rotational characteristics of the motor are improved.
To solve the above and/or other problems, it is an aspect to provide a brushless vibration motor generating a stable vibration and improving durability using an improved assembling structure of a rotor eccentrically rotating in the brushless vibration motor.
It is another aspect of the invention to provide a brushless vibration motor compatible with mobile telecommunication machines having different type of vibration methods of a vibration motor, reducing a manufacturing cost in integrally assembling electrical driving parts of the brushless vibration motor, and improving an assembling structure of a rotor.
It is another aspect of the invention to provide a brushless vibration motor having a cogging generating unit preventing a non-motive point occurring when the brushless vibration motor is a mono phase type, by reducing an assembling structure of a rotor.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and/or other aspects, a brushless vibration motor includes a base plate unit having a burring element extended from the base plate and a shaft having a first portion inserted into the burring element to be fixedly coupled to the base plate, a stator having at least one coil disposed on the base plate through which current flows, a rotor rotatably supported by a second portion of the shaft and having a bearing slidably inserted around the second portion of the shaft, a bearing holder having an inside surface forcibly coupled to the bearing, and a yoke coupled to the bearing holder and having a magnet mounted on the yoke to be spaced-apart from the coils to generate a magnetic field with the coil, and a counterweight generating eccentricity, and a cover coupled to the base plate to enclose the stator and the rotor.
According to another aspect to the present invention, the bearing holder forms a space with the bearing forcibly inserted into the bearing holder, and the rotor includes a thrust washer inserted into the space and supported by the second portion of the shaft.
According to another aspect to the present invention, the second end of the shaft includes a distal end formed on the second portion and having a curvature to come into point-contact with the thrust washer to support the thrust washer.
According to another aspect to the present invention, the rotor includes a wall defining the space and a hole formed on the wall through which the space communicate with an outside of the bearing holder.
According to another aspect to the present invention, the yoke is formed of a soft magnetic material.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, another inside surface forming a space with the bearing, and a thrust washer inserted into the space and supported by a round end of the second portion of the shaft, and the yoke includes a first yoke forcibly inserted around an outside surface of the bearing holder, and having the counterweight formed on a portion of the upper yoke, and a second yoke forcibly inserted around the outside surface of the bearing holder, and having a ring type magnet.
According to another aspect to the present invention, the second yoke is formed of a soft magnetic material.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, another inside surface forming a space with the bearing, and a thrust washer inserted into the space and supported by a round end of the second portion of the shaft, and the yoke is forcibly inserted around an outside surface of the bearing holder to be fixedly coupled to the bearing holder and includes a first portion limiting a movement of the counterweight with the bearing holder in an axial direction and in a radial direction of the shaft, and a second portion mounted with the magnet having a ring type.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, another inside surface forming a space with the bearing, and a thrust washer inserted into the space and supported by a round end of the second portion of the shaft, and the yoke includes a first yoke forcibly inserted around an outside surface of the bearing holder and formed asymmetrically with respect to the shaft to eccentrically rotate the rotor, and a second yoke forcibly inserted around the outside surface of the bearing holder and formed with the magnet having a ring type.
According to another aspect to the present invention, the second yoke is formed of a soft magnetic material.
According to another aspect to the present invention, the first yoke is formed of a metal having a specific gravity of less than 10.
According to another aspect to the present invention, the bearing holder comprises a cap shape having an opening open to the base plate, the yoke is coupled to an upper surface of the bearing holder, the magnet is a ring-type disposed on the yoke, and the counterweight is disposed on the yoke.
According to another aspect to the present invention, the yoke forms a space with the bearing holder, and the rotor includes a hole formed on a portion of the bearing holder to communicate with the space and an outside of the bearing holder, and a thrust washer having one portion inserted into the hole and the other portion disposed in the space between the portion of the bearing holder and the shaft to be supported by a curved end of the second portion of the shaft.
According to another aspect to the present invention, the rotor includes an air circulation hole formed on one of the bearing holder and the thrust washer and communicating with a space surrounded by the bearing, the thrust washer, and the shaft.
According to another aspect to the present invention, the yoke includes a circumference bent toward the base plate, the magnet includes an inner surface supported by an outer surface of the bearing holder and disposed on the yoke, and the counterweight includes a protrusion having a step shape in an radial direction of the shaft and disposed between an outer circumferential surface of the magnet and an inside surface of the circumference of the yoke.
According to another aspect to the present invention, the motor is a mono phase drive type having a non-motive point, and the rotor includes a cogging torque generating unit disposed on one of the base plate and the cover to prevent the non-motive point.
According to another aspect to the present invention, the magnet includes a plurality of magnetic poles having a first angle with respect to the shaft, the coil includes a center line extended from the shaft, and the cogging torque generating unit is disposed on a line forming a second angle of a quarter of the first angle of the coil with respect to the center line of the coil.
According to another aspect to the present invention, the magnet includes 6 magnetic poles, the coil comprises a center line extended from the shaft, and the cogging torque generating unit is disposed on a line having an angle of 15 degrees with respect to the center line of the coil.
According to another aspect to the present invention, the magnet includes 6 magnetic poles, the coil comprises sub-coils each having a center line extended from the shaft, and the cogging torque generating unit includes sub-cogging torque generating units each disposed on a line having an angle of 15 degrees with respect to corresponding center line of the sub-coils.
To achieve the above and/or other objects, a brushless vibration motor includes a base plate unit having a burring element extended from the base plate and a shaft having a first portion inserted into the burring element to be fixedly coupled to the base plate, a stator having at least one coil disposed on a first area of the base plate through which current flows, a rotor rotatably supported by a second portion of the shaft and having a bearing slidably inserted around the second portion of the shaft, a bearing holder having an inside surface forcibly coupled to the bearing, and a yoke coupled to the bearing holder and having a magnet mounted on the yoke to be spaced-apart from the coils to generate a magnetic field with the coil, and a counterweight generating eccentricity, a motor drive IC disposed on a second area of the base plate to face the rotor and to control the current flowing through the coil, and a cover coupled to the base plate to enclose the stator, the rotor, and the motor drive IC.
According to another aspect to the present invention, the stator includes a hall element formed in the motor drive IC in a single body to detect polarity of the magnet.
According to another aspect to the present invention, the base plate includes a first side facing the rotor and a second side disposed opposite to the first side, and the stator includes a printed circuit board disposed on the first side of the base plate and mounted with the coil and the motor drive IC.
According to another aspect to the present invention, the base plate includes a terminal unit formed on one of the first and second sides of the base plate, coupled to the printed circuit board, and coupled to an external source to receive the current.
According to another aspect to the present invention, the stator includes another printed circuit board disposed on one of the first and second sides of the base plate, coupled to an external source to receive the current, and coupled to the printed circuit board having the coil and the motor drive IC.
According to another aspect to the present invention, the base plate includes one of a single printed circuit board and a double-sided printed circuit board.
According to another aspect to the present invention, the bearing holder forms a space with the bearing forcibly inserted into the bearing holder, and the rotor includes a thrust washer inserted into the space and supported by the second portion of the shaft.
According to another aspect to the present invention, the second end of the shaft includes a distal end formed on the second portion and having a curvature to come into point-contact with the thrust washer to support the thrust washer.
According to another aspect to the present invention, the rotor includes a wall defining the space, and a hole formed on the wall through which the space communicate with an outside of the bearing holder.
According to another aspect to the present invention, the yoke is formed of a soft magnetic material.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, another inside surface forming a space with the bearing, and a thrust washer inserted into the space and supported by a round end of the second portion of the shaft, and the yoke includes a first yoke forcibly inserted around an outside surface of the bearing holder, and having the counterweight formed on a portion of the upper yoke, and a second yoke forcibly inserted around the outside surface of the bearing holder, and having a ring type magnet.
According to another aspect to the present invention, the second yoke is formed of a soft magnetic material.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, another inside surface forming a space with the bearing, and a thrust washer inserted into the space and supported by a round end of the second portion of the shaft, and the yoke is forcibly inserted around an outside surface of the bearing holder to be fixedly coupled to the bearing holder and includes a first portion limiting a movement of the counterweight with the bearing holder in an axial direction and in a radial direction of the shaft, and a second portion mounted with the magnet having a ring type.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, another inside surface forming a space with the bearing, and a thrust washer inserted into the space and supported by a round end of the second portion of the shaft, and the yoke includes a first yoke forcibly inserted around an outside surface of the bearing holder and formed asymmetrically with respect to the shaft to eccentrically rotate the rotor, and a second yoke forcibly inserted around the outside surface of the bearing holder and formed with the magnet having a ring type.
According to another aspect to the present invention, the second yoke is formed of a soft magnetic material.
According to another aspect to the present invention, the first yoke is formed of a metal having a specific gravity of less than 10.
According to another aspect to the present invention, the bearing holder includes a cap shape having an opening open to the base plate, the yoke is coupled to an upper surface of the bearing holder, the magnet is a ring-type disposed on the yoke, and the counterweight is disposed on the yoke.
According to another aspect to the present invention, the yoke forms a space with the bearing holder, and the rotor includes a hole formed on a portion of the bearing holder to communicate with the space and an outside of the bearing holder, and a thrust washer having one portion inserted into the hole and the other portion disposed in the space between the portion of the bearing holder and the shaft to be supported by a curved end of the second portion of the shaft.
According to another aspect to the present invention, the rotor includes an air circulation hole formed on one of the bearing holder and the thrust washer and communicating with a space surrounded by the bearing, the thrust washer, and the shaft.
According to another aspect to the present invention, the yoke includes a circumference bent toward the base plate, the magnet includes an inner surface supported by an outer surface of the bearing holder and disposed on the yoke, and the counterweight includes a protrusion having a step shape in an radial direction of the shaft and disposed between an outer circumferential surface of the magnet and an inside surface of the circumference of the yoke.
According to another aspect to the present invention, the motor is a mono phase drive type having a non-motive point, and the rotor includes a cogging torque generating unit disposed on one of the base plate and the cover to prevent the non-motive point.
According to another aspect to the present invention, the magnet includes a plurality of magnetic poles having a first angle with respect to the shaft, the coil includes a center line extended from the shaft, and the cogging torque generating unit is disposed on a line forming a second angle of a quarter of the first angle of the coil with respect to the center line of the coil.
According to another aspect to the present invention, the magnet includes 6 magnetic poles, the coil includes a center line extended from the shaft, and the cogging torque generating unit is disposed on a line having an angle of 15 degrees with respect to the center line of the coil.
According to another aspect to the present invention, the magnet includes 6 magnetic poles, the coil comprises sub-coils each having a center line extended from the shaft, and the cogging torque generating unit includes sub-cogging torque generating units each disposed on a line having an angle of 15 degrees with respect to corresponding center line of the sub-coils.